Step-by-step instructions for building a strip foundation with your own hands + basic installation errors

A strip foundation’s construction is an essential first step toward guaranteeing any structure’s longevity and stability. Correct foundation construction is crucial, regardless of the size of the building project—from a small shed to a larger home. You can save time and money by building a sturdy and dependable strip foundation yourself with a few simple tools and supplies.

This manual will take you step-by-step through the entire process, from preparation and excavation to concrete pouring and foundation finishing. We’ll give you simple, understandable instructions that will help you stay out of trouble and make sure your project turns out well.

Along with providing detailed instructions, we’ll also point out some of the most typical mistakes that people make when putting in a strip foundation. By being aware of these mistakes, you can prevent them and produce work that looks more professional. You will acquire the self-assurance and expertise required to lay a strong foundation for your construction project by adhering to this guide.

Step	Description
1. Planning	Design the foundation layout and determine dimensions. Obtain necessary permits.
2. Excavation	Dig a trench to the required depth and width for the foundation.
3. Install Formwork	Set up wooden or metal forms to shape the concrete pour.
4. Add Reinforcement	Place steel rebar within the formwork to strengthen the foundation.
5. Pour Concrete	Mix and pour concrete into the formwork, ensuring even distribution.
6. Curing	Allow the concrete to cure for the recommended period, keeping it moist.
7. Remove Formwork	Carefully remove the formwork once the concrete has sufficiently cured.
8. Backfilling	Fill in the trench around the foundation with soil, compacting it properly.
Common Installation Errors	Description
Incorrect Dimensions	Failing to follow the design dimensions can weaken the foundation.
Poor Reinforcement Placement	Improper rebar placement can lead to cracks and structural issues.
Insufficient Curing	Not allowing the concrete to cure properly can reduce its strength.
Improper Backfilling	Not compacting soil around the foundation can cause settling and instability.

Types

A solid closed support structure beneath all exterior and interior load-bearing walls is called a strip foundation. This is actually a recessed basement that can withstand loads from the building’s weight, soil pressure, and other impacts.

The strip foundation types are as follows:

• Monolithic. It is a solid casting of reinforced concrete, has maximum strength and bearing capacity.
• Prefabricated. The strip is built from individual fragments or elements – foundation blocks (FBS), brick, natural stone, etc.. The performance characteristics of this type of foundation are slightly lower than those of a monolithic strip.
• Combined. It is a combination of a strip base with another type – for example, pile-tape. Allows you to obtain reference points on which the supporting belt is installed.

Furthermore, there are differences in depth:

• Non-buried. Created on absolutely motionless soils – rocks, strong stable soils. Very rare.
• Shallow. Used for construction on durable soils not subject to frost heaving. The depth is less than the level of winter soil freezing.
• Recessed. The depth of laying such a tape is slightly below the soil freezing level. Used for the most massive and heavy buildings, suitable for most types of soil and hydrogeological conditions.

An examination of every aspect of the site, including the soil’s composition, quantity and characteristics of its layers, soil water content, etc., is necessary to choose the right kind.

What buildings is it suitable for?

Strip foundations provide sturdy support for a variety of building materials:

• Tree.
• Foam and aerated concrete.
• Brick.
• Concrete plates.

The building’s weight is determined by its material and floor count, which also affects the tape’s design parameters, such as thickness and depth. The building parameters are the primary source of information used in engineering calculations during design, along with the properties of the soil.

You can save money and feel proud of yourself for doing a good job when you build your own strip foundation, but it’s crucial to pay close attention to every detail to guarantee a sturdy, long-lasting foundation. From planning and digging to pouring concrete and curing, this guide will take you step-by-step through the entire process, pointing out typical pitfalls to watch out for along the way. Your construction project will have a solid, dependable foundation if you adhere to these detailed instructions and watch out for any potential hazards.

How to calculate depth

The type of foundation determines how to calculate the strip foundation’s depth. If buried construction is the preferred method, then the tabular data from SNiP, which shows the depth of soil freezing in a specific area, must be used.

Groundwater presence and depth, as well as soil composition, are considered when building a shallow type of belt. Although 0.75 to 1 m is typically thought to be the ideal depth, it can be slightly less on dry, stable soils.

How is a shallow strip foundation constructed?

With a lesser degree of immersion, the shallow strip foundation essentially mimics the buried version.

A concrete strip is poured in a trench that has a drainage layer of backfill created in it.

Shallow foundation designs are less capable than full-fledged tape designs, but they are still quite adequate for relatively small low-rise buildings in terms of load-bearing capacity.

Step-by-step DIY installation instructions

Now let’s look at how a strip foundation is made:

• Preparation.
• Site marking.
• Digging a trench.
• Laying and arrangement of the drainage system.
• Creating a sand cushion.
• Manufacturing of formwork.
• Installation of reinforcement cage.
• Pouring concrete.
• Waiting time for hardening.
• Stripping.
• Waterproofing and insulation tape.
• Further work.

Since every stage is the result of an earlier operation, the sequence of events remains constant in almost all cases.

Surface marking

The first step in the process is to mark the area and remove the top layer of soil. Wooden stakes are used for this purpose, and they are positioned at the future trench’s intersections and corners.

The width is chosen using the base’s computed parameters, but it must be at least 20 centimeters wider than the tape. This is crucial because it will be required to set up formwork within the trench and then make sure that the backfill layer is thick enough to accommodate the sinuses.

Preparing the trench

You can dig a trench by hand or with an excavator. Although the second option is challenging, it is conceivable if issues occur with the delivery or approach of construction equipment to the site. The earth that has been excavated is either immediately removed from the site or stored on the trench’s sides.

While maintaining the same depth is essential, leveling the bottom to a centimeter is not something that has to be done too forcefully. Regardless of the digging technique, trench corners are manually aligned.

Drainage device

By removing groundwater from the sand cushion layer, the drainage system makes it impossible for heaving loads to happen during the winter.

There are various kinds of systems, including:

• Open. Created on the day surface and designed to drain rain or melt water. Used on dry soils with deep groundwater.
• Closed.Consists of a pipeline system placed in a trench close to the belt. Serves to remove groundwater from a layer of sand backfill (pillow), used on soils with the presence or seasonal changes in the level of soil water.

Since there is typically a risk of water leakage, the closed type is utilized in practice the most. A drainage well is supplied with moisture through a network of specially designed pipelines.

A slope for the natural flow of water and the installation of filtration pipework are prerequisites for the proper operation of high-quality drainage. By removing tiny organic particles, the filtration layer keeps the drainage pipes’ interior surfaces from silting.

This lowers the chance of failures and helps the system last longer.

Pillow

A crucial and necessary component of the foundation is the sand cushion. Although it varies, its average thickness is 20 cm. Typically, five centimeters of leveling sand is used, followed by ten centimeters of finely crushed stone, ten centimeters of sand, and finally, clean river sand.

Vibrating machines or hand tools are used in careful compaction after each layer has been filled. It is advised to remove the layers using water as this improves the pillow’s sealing.

When assessing the quality of compaction of the backfill layer, experts advise following these guidelines: there shouldn’t be any evidence of shoes left on the ground from walking. This is crucial because cushion settlement deforms the tape and has unpredictable results, which is unacceptable.

Installation of formwork

Depending on the size of the tape, edged boards with a thickness of 25–40 mm are used to create formwork. Shields are first put together adjacent to the trench, their width just barely bigger than the tape’s height. The shields are assembled, lowered into the trench, and secured from the exterior using vertical support strips and inclined stops.

The width of the tape is equal to the distance between the panels, which is determined by installing crossbars from the inside. When pouring and setting concrete, the formwork needs to be sturdy and able to support weights. No gaps should exist; any that are bigger than 3 mm need to be sealed with tow or blocked with slats.

This will stop concrete from being wasted when it leaks into the cracks.

Reinforcement

The purpose of the reinforcement is to offset tensile axial loads that the concrete is unable to support. Even with heavy pressure, it easily breaks when bent because the tape is unstable.

Horizontal working rods made of metal or fiberglass ribbed reinforcement are the primary component of a reinforcing belt, which is made for reinforcement.

Smooth rods with a smaller diameter are used to hold the rods in the desired position. From these rods, vertical elements, or clamps, are formed, which together with the working rods form a spatial lattice.

Because of its dimensions, the horizontal rods are submerged in the concrete between two and five centimeters deep.

The width of the tape is used to determine which working rods to use. Their diameter ranges from 12 to 14 mm for a shallow base (width of 30 to 40 cm) or 16 mm for a wider base.

Knitting reinforcement

There are two methods for connecting reinforcement frame elements:

• Electric welding.
• Knitting with soft steel annealed wire.

When building shallow foundations, the first option is essentially never used and is reserved for thick rods. The most common method for assembling the arm belt is knitting.

The frame elements are held together quite firmly by a soft wire that allows for some degree of flexibility while still allowing the frame to remain intact when loads are applied during pouring.

For knitting, a unique hook-shaped tool is utilized. A 25–30 cm length of wire is folded in half. The resulting half-loop rises at the ends and wraps diagonally around both connected rods.

Next, using a hook to grasp the fold loop, rotate the two rods three times while leaning on the second free end. This will ensure that the rods are securely attached to one another.

The process is straightforward, and on the first day, the skill is typically developed.

Selecting concrete for pouring

Concrete comes in a variety of grades that are intended for use with various loads and circumstances. Since low-rise private construction is the primary application for shallow strip foundations, concrete grade M200 would be the best option.

With a comparatively small dead weight, it can supply the belt’s required strength and load-bearing capacity.

We suggest using an online calculator to determine the grade and quantity of concrete for individuals who would prefer to handle the problem more methodically. To guard against potential mistakes, you should replicate the outcome on a different resource.

Fill

Filling needs to be completed as soon as possible, ideally concurrently. It is not acceptable to stop pouring concrete for longer than a day; in these situations, the concrete must be left until it solidifies completely before proceeding with the work. Such a tape has substantially less strength and quality than simultaneous casting.

The easiest way to satisfy this requirement is to use ready-mixed concrete, which is transported in a mixer right to the pouring location. In any case, the concrete will be of higher quality than a homemade solution, and there will be a significant time savings as a result.

Pouring must be done from multiple locations, attempting to disperse the contents as uniformly as possible along the tape’s length. This will enable you to get a casting with the same specifications all the way around, guaranteeing the base’s high strength.

Features of waterproofing

Shallow tape is severely harmed by moisture exposure. Water seeps into concrete and eventually freezes, tearing the material from the inside out. In any case, this shouldn’t be permitted.

You can apply waterproofing in two different ways:

• Horizontal. Protects the lower and upper plane of the tape from moisture penetration from the lower layers of soil and from rain or melt water flowing down the walls. The lower waterproofing is laid before installing the formwork and reinforcement belt, and the upper one is done after the concrete has completely hardened in parallel with the vertical waterproofing. Both layers consist of roofing felt laid in two layers with a coating of bitumen mastic.
• Vertical. Applied to the outer and inner surfaces of the tape after stripping and complete drying. Materials of different types of action are used – impregnations, coatings or adhesives. Impregnations are the most effective, but they appeared relatively recently and are little known to builders.

Insulation issues

Condensation cannot occur because the tape is insulated. Insulation can be done internally or externally. The insulation is mounted from the outside in the first instance and from the inside in the second.

It is impossible to get the desired outcome by doing both types of insulation separately, so experts advise doing them both at once. It is imperative to utilize moisture-resistant heat insulators such as polyethylene foam, liquid polyurethane foam, foundation penoplex, etc., while considering the placement details.

In this situation, mineral wool should not be used since it can absorb water and become completely inoperable.

Proper care of concrete after pouring

For ten days following the pour, the tape’s surface must be consistently misted with water:

• The first 3 days – every 4 hours.
• The next 7 days – 3 times a day.

The tape needs to be covered in a layer of polyethylene to protect it from the sun’s glaring rays. By watering the tape, you can reduce loads and the chance of cracks by achieving a somewhat equal moisture content in the inner and outer layers.

Although it takes a long time for the concrete to fully harden, you can still use the tape after 28 days.

Stripping

Formwork is taken apart using a process called ringing. No sooner than ten days following the pouring can it be completed.

The foundation is too important a component of the construction to take chances with and rely on accident, so you shouldn’t try to rush it.

Basic errors

The majority of the time, a sandy pillow’s sedimentation is caused by a poorly made sealing layer of filling. Furthermore, it is frequently observed that improper materials are used, specifically incorrectly branded concrete.

Certain dishonest vendors provide inferior material in order to save money. Experts with experience advise getting more severe concrete; order M250 rather than M200. Although there isn’t much of a cost or mass difference, the material might be more resilient.

Furthermore, they frequently give up on insulation and waterproofing in an effort to save money and labor. These processes take time, but they are completed very quickly in relation to the base’s service life, so they cannot be disregarded.

Useful video

You will discover how to install a strip foundation by watching this video:

Doing your own strip foundation construction can be a gratifying project that saves money and gives your construction a solid foundation. You can be sure that you’ve covered everything by following a step-by-step guide, from site preparation to concrete pouring. By taking your time to comprehend and carry out each step, you can avoid common pitfalls and build a strong, long-lasting foundation.

Accurate measurement and site preparation are essential first steps. Any errors made now could later cause more serious issues. Establishing the proper depth, width, and levelness of the trenches is crucial for achieving success. The durability and strength of the foundation also depend on using premium materials and properly mixing the concrete.

Bad placement of reinforcement is one of the most frequent mistakes. Verify that the rebar is properly positioned and fastened. This stops cracks and gives the required strength. Don’t forget to consider the curing process. Even though you’re excited to get on to the next stage of your project, give the concrete enough time to properly harden.

Lastly, keep in mind that the details are crucial. Verifying everything twice—from alignment to measurements—can help you avoid making expensive errors. Although constructing a strip foundation is a big job, you can do it yourself and get a finished product that looks professional. You’ll have no trouble building a successful project if you keep these pointers in mind.

Video on the topic

Ties for rebar formwork. Taken during the construction of the strip foundation. #construction

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